Method for continuous production of coke and heat



Aug. 22, 1961 v. MANSFIELD 2,997,426

METHOD FOR CONTINUOUS PRODUCTION OF COKE. AND HEAT Filed Nov. 2, 1959 PEI/WAR) AIR INVENTOR BY QMAH'iW ATTORNEY 2,997,426 METHOD FOR CONTINUOUS PRODUCTION OF COKE AND HEAT Vaughn Mansfield, 5340 Delmar Blvd., St. Louis, Mo. Filed Nov. 2, 1959, Ser. No. 850,361 5 Claims. (Cl. '2026) This invention relates to a continuous method for producing coke and boiler heat on a traveling grate stoker.

The patents to Anderson et al., Nos. 2,209,225 and 2,380,930; relate to continuous coke production wherein a relatively thin bed of coal is moved on a chain grate through a coking oven, and air is fed only upwardly through the grate in such small amounts that limited combustion of the volatiles in the coal takes place. As the bed slowly advances through the oven, coking temperatures slowly develop throughout the bed, until the volatiles are driven off and the coal is sufficiently carbonized. The objects of this invention are: To speed up the rate of carbonization; to produce heat which may be utilized in a furnace or the like heat-consuming device; and to improve the structure and strength of the coke. The basic coking oven structure utilized for these improvements in the process is generally similar to that in the patent to Anderson et al., No. 2,380,930, except in that a much thicker fuel bed is formed, and there is provided a means for feeding over-fire air into the oven, at a flue mouth, so as to create a fireball over the bed. The new objects are: To produce radiant heat over the traveling bed and thereby heat it to plasticity much quicker; to utilize the weight of the fuel in the bed in order to densify and compact the plasticised mass; and to provide the fireball and hot exhaust gases rising above it for utilization in a boiler or the like conventional heat using device. By utilizing the volatiles, which are driven off the coking bed, as fuel for burning with the over-fire air, the dual purposes of rapid coking by radiant heat, and utilizable heat production are served.

Another object is to recycle hot stack gas through the hot coal bed on a travelling grate stoker for sweeping off volatiles and then feeding over-fire air so as to burn the volatiles above the bed. In this manner it is intended to produce minimal burning within the bed; to subject the coal on the grate to radiant heat from above the bed; and to utilize the coal on the grate for shielding the grate from the high temperatures developed above the bed.

Still another object is to provide a coke and heat producing system which includes a coking oven in which the coal is not completely carbonized, and a coke cooker in which devolatilization is completed, wherein the residual volatiles are driven off the coke in the cooker and returned for burning in the oven, wherein stack gases from the oven are recycled and cooled for cooling the coke in the cooker, and wherein heat extracted when cooling the stack gases is utilized for pre-heating the under-fire and over-fire air supplied to the oven.

These and other objects will be apparent from the following specification and drawing, in which the sole figure is a diagrammatic cross section through the coking oven and cooker in which the subject invention is practiced and embodied.

Referring now to the drawing in which like reference numerals denote similar elements, the coking oven is disposed beneath the furnace 12 in which heat is utilized and the output end of the coking oven, on the right hand side of the drawing, discharges into a combined coke cooker and quenching retort 14. Green coal, having a coke button higher than 2 /2, and permissibly quite small in size, down to A by 0, is supplied from the hopper 16 to a preheater 18, in which all moisture is driven off, and in which the coal is completely dried and preheated to approximately 350 F. From preheater 18 the coal is States Patent ice discharged into a hopper 20 whose outflow is controlled by a spreader gate 22 so that the coal forms a relatively thick bed 24 on a travelling grate stoker 26. A conventional igniter 28 at the lower end of the front arch 30 of oven 10 may be utilized for partly igniting the coal on bed 24 as the coal starts through the oven. After being ignited, the coal passes beneath the furnace mouth 32, and then under the rear arch 34 of the oven and, after travelling the full length of the top run of the travelling grate stoker 26, the nearly completely carbonized coke drops through an oven outlet 36 which constitutes also the inlet of retort 14. The coke from oven 10 fills the retort so as to form a column therein, and the column moves slowly downwardly to the lower end of the retort from which it is discharged by a substantially air tight screw conveyor 38.

Between the upper and lower runs of the travelling grate stoker 26 is mounted an air box 40 which is transversely partitioned to provide eight zones, 1 to 8, respectively, progressing from the input end of oven 10 towards the output end. Air pipes AP individually controlled by valves supply preheated air to the air box zones from a manifold 42, the preheated air being supplied to the manifold through a line 46 which leads from an air preheater 48. Air is derived from a supply line 50 and is forced through the preheater and into manifold 42 by a pump 52. Also leading frommanifold 42 is an over-fire air supply line 54 through which preheated air is supplied to over-fire air ports 56- in the sides of oven 10', beneath rear arch 34, and to jets 58 disposed just below the mouth 32 of furnace 12.

The details of furnace 12 form no part of the subject invention, it being sufficient to note that after the heat resulting from the combustion of gases rising from oven 12 is utilized, and that the stack gases exhausted through the furnace stack, diagrammatically indicated at 60, still contain sufficient heat for preheating the green coal. Some of the hot stack gases are taken from stack 60 through a supply line 62 and forced by pump 64 through coal preheater 18 and returned to the stack through a line diagrammatically indicated at 66. Other hot stack gases are carried from stack 60 through a line diagrammatically indicated at 68 and forced by a pump 70 to a stack gas manifold 72. Some of the hot stack gasese are fed from manifold 72 through gas pipes GP, individually controlled by valves, to the individual zones in.air box 40. Other hot stack gases from manifold 72 are fed by a line 74, controlled by valve 76, into a gas line 78 which leads from'air preheater 48 and forms a part of a substantially closed circulatory system through which the gases are forced by pump 80 to a manifold 82 surrounding the lower end of retort 14. From manifold 82 the gases pass through ports 84 into the lower end of retort 14, and flow upwardly through the lower portion 86 of the retort. Most of the gases entering through ports 84 are drawn off through ports 88 in the side of the retort, into a manifold 90 and, through a return line 92 back through air preheater 48 wherein heat is transferred to the primary air flowing from preheater 48 through line 46 to manifold 42. In starting the system valve 76 is opened sufiiciently to charge the substantially closed circuit which includes :line 78, pump 80, manifold 82, the lower portion 86 of retort 14, manifold 90, return line 92 and air preheater 48. Thereafter, valve 76 is nearly closed so that only enough hot stack gases, which are nearly inert, and bled into line 78 to make up the small losses resulting from the escape of gases upwardly through the upper portion 93 of retort 14. The gases escaping upwardly through the upper portion 93 of the retort sweep off the residual volatiles and return them into oven 10.

In starting the process, preheated coal from hopper 20 is ignited by igniter 28 as the coal starts through the oven 3 on travelling grate stoker 26. All of the valvm in air pipes AP are opened to supply under-fire air through zones 1 to 8, inclusive, of air box 40 so as to burn the coal sufficiently to preheat the oven, the ash dropping-01f the end of the stoker through retort 14 and thence being discharged by screw conveyor 38. After the oven has been preheated, the valves in air pipes AP leading to zones 7 and 8 are closed and the valve in the air pipes leading to zones 1 to 6 are partly closed, in progressive amounts, so that only a limited amount of air is supplied to air box zone 1, and progressively lesser amounts of air are sup plied to zones 2 to 6, inclusive. The coal bed, being between 6 /2" and 24" in depth, is comparatively thick and the coal, relatively small in size, forms a dense heavy mass. Ignition starts at the top of the bed as the latter progresses over air box zone 1; and works downwardly through the bed to the bottom as the bed progresses through the oven. The bed temperature, however, progressively rises as the coal bed moves through oven 10 as follows: The valves in gas pipes GP are opened so as to supply hot stack gases to the air box zones in increasingly large amounts, progressing from zone 1 through to zone 8. As the bed passes over air box zone 1, the temperature of the coal is raised from its starting temperature, about 350 P, so that, by the time the bed starts over zone 2, the bed temperature, at least at and near the top, has reached about 848 F and the coal in the bed has started to become plastic. Only enough air is supplied to burn the low-temperature volatiles sufficient to raise the bed temperature and substantial amounts of volatiles are swept upwardly through the bed. While insufi'icient under-fire air is supplied to burn the upwardly swept volatiles, valves 98, controlling the supply of preheated air through jets 58 are opened and suffioient air is fed into the oven beneath the mouth 32 of furnace 12 to burn with the upswept volatiles and start a fireball 96 over the coal bed. The heat from fireball 96, whose temperature is about 2,400 B, radiates downwardly onto the bed so that as the bed progresses over zone 2 the bed temperature, near the top of the bed, starts rising from about 848 F. and, by the time the bed has progressed over air box zone 3, the maximum temperature is about 1,060" F. As the bed temperature rises, additional volatile matter is swept upwardly by the hot stack gases from manifold 72. Air valves 98 meanwhile have been opened to supply overfire air through ports 56 which lie above zones 4 to 8, inclusive, so as to burn with the upswept volatiles, thereby extending fireball Q6 over virtually the entire coal bed passing through oven 10-. While rear arch 34 is shown as a straight downwardly sloping structure, its specific shape and the resultant volume of the oven above the coal bed will be devised in relation to the heat release, according to known principles of furnace construction.

The temperature of the bed, upon passing over zone 6 having been raised to the range of 1,800 F. to 1900 F., and the bed then being heated through from top to bottom, the valves in air pipes AP leading to air box zones 7 and 3 are closed so that no air is fed to the now incandescent bed, and only preheated stack gases are fed upwardly through the bed as it passes over air box zones 7 and 8. Over zones 7 and 8, most of the remaining volatiles in the coal are driven off by the heat which has been developed in the bed. Meanwhile, by the time the coal bed passed over zone 3, it had become completely plasticized and the weight of the coal itself compacted the coal in all but the upper strata of the bed, so that a strong, compact incandescent coke falls into retort 14 and forms a column nearly to the top of the retort The coke dropping into retort 93 still contains residual volatiles which, if exposed to the heat in the incandescent coke about l,800 to 1,900 P. for a suflicient length of time would be driven off. These residual volatiles are driven oifthe coke, as the column progresses downwardly through the upper portion 93 of retort 14, the volatiles drift back into oven 10 where they are consumed in fireball 96. As the column then progresses downwardly through the lower portion 86 of retort 14, heat is extracted by the cool stack gases which flow in through ports 84 near the bottom of retort 14, upwardly through lower portion 86, and outwardly through ports 88 and back to primary air preheater 48. Thus, when the coke is discharged from the bottom of retort 14 by screw conveyor 38, it will have been cooled to well below its ignition point, so that it may be exposed to air and easily handled. The retort per se is disclosed and claimed in the joint application of McCollurn and Mansfield, Serial No. 820,- 172, filed June 15, 1959, and entitled Coke Quenching Retort and Method, and now abandoned.

The invention is not limited to the details of the apparatus and method herein disclosed, but is intended to cover all substitutions, modifications and equivalents within the scope of the following claims.

I claim:

1. In a method of producing heat and coke from green plasticisable coking coal, including the steps of preheating the coal until substantially all moisture is driven therefrom and the coal is dry; passing a homogeneous bed of the dried preheated coal in a horizontal path through a coking oven having a furnace month over part of the bed path; and igniting part of the bed as it enters the oven: the improvements which comprise the steps of zone feeding hot primary air upwardly through the bed from an initial zonal region beneath the bed at the start of the path in amounts sufficient to completely ignite the bed but insufficient to combust with a substantial portion of the volatiles liberated from the coal thereabove; simultaneously zone feeding hot primary air upwardly through the bed from succeeding zonal regions disposed beneath the bed progressively away from the initial zonal region and towards the end of the path in successively decreasing amounts suflicient to maintain limited combustion within the bed but insuflicient to combust with substantial portions of the volatiles liberated from the coal thereabove; simultaneously zone feeding hot, substantially oxygen-free gas upwardly through the bed with said decreasing amounts of air in progressively increasing amounts from said succeeding zonal regions so as to sweep unburned volatiles into the oven above the bed; and simultaneously feeding hot over-fire air into said oven to combust with said unburned volatiles and thereby create a fireball over the bed and in the furnace mouth, the partial combustion of the unburned volatiles in the bed and the radiation of the fireball heating the coal in the bed progressively upward to maximum temperatures in the range of 1,800 to l,900 F.

2. In a method of producing heat and coke from plasticisable coking coal, including the steps of preheating the coal to about 350 F.; passing a homogeneous bed of the preheated coal in a horizontal path through a coking oven having a furnace month over part of the bed path; and igniting part of the bed as it enters the oven: the improvements which comprise the steps of zone feeding hot primary air upwardly through the bed from an initial zonal region beneath the bed at the start of the path in amounts sufiicient to completely ignite the bed but insuflicient to combust with a substantial portion of the volatiles liberated from the coal thereabove; simultaneously zone feeding hot primary air upwardly through the bed from succeeding zonal regions disposed beneath the bed path progressively away from the initial zonal region and towards the end of the path in successively decreasing amounts suflicient to maintain limited combustion within the bed but insufficient to combust with substantial portions of the volatiles liberated from the coal thereabove; simultaneously zone feeding hot, substantially oxygen-free gas upwardly through the bed with said decreasing amounts of air in progressively increasing amounts from said succeeding zonal regions and simultaneously zone feeding hot substantially oxygen-free gas alone upwardly through the bed from a terminal zonal region beneath the bed at the end of the path so as to sweep unburned volatiles into the oven above the bed; and simultaneously feeding hot over-fire air into said oven to combust with said unburned volatiles and thereby create a fireball over the bed and in the furnace mouth, the partial combustion of the unburned volatiles in the bed and the radiation of the fireball heating the coal in the bed progressively upward to maximum temperatures in the range of l,800 F. to 1,900 F.

3. In a method of producing heat and coke from plasticisable coking coal, including the steps of preheating the coal to about 350 F.; passing a relatively thick homogeneous bed of the preheated coal in a hori zontal path through a coking oven having a furnace mouth over part of the bed path; and igniting the bed as it enters the oven: the improveemnts which comprise the steps of zone feeding hot primary air upwardly through the bed from an initial zonal region beneath the bed at the start of the path in amounts sufiicient to raise the bed temperature to approximately 600 F., but insufficient to combust with a substantial portion of the volatiles liberated from the coal thereabove; simultaneously zone feeding hot primary air upwardly through the bed from succeeding zonal regions disposed beneath the bed progressively away from the initial zonal region and towards the end of the bed path in successively decreasing amounts sufiicient to maintain limited combustion within the bed but insufiicient to combust with substantial portions of the volatiles liberated from the coal thereabove; simultaneously feeding hot, substantially oxygen-free gas upwardly through the bed with said successively decreasing amounts of air in progressively increasing amounts from said succeeding zonal regions so as to sweep unburned volatiles into the oven above the bed, and simultaneously feeding hot over-fire air into said oven to combust with said unburned volatiles and thereby create a fireball over the bed and in the furnace mouth, the partial combustion of the unburned volatiles in the bed and the radiation of the fireball heating the coal in the bed progressively upward to maximum temperatures in the range of 1,800 F. to 1,900 F.

4. In a method of producing heat and coke from plasticisable coking coal, including the steps of preheating the coal until substantially all moisture is driven therefrom and the coal is dry; passing a homogeneous bed of the dried preheated coal in a horizontal path through a coking oven having a furnace mouth over part of the bed path; and igniting part of the bed as it enters the oven: the improvements which comprise the steps of zone feeding hot primary air upwardly through the bed from an initial zonal region beneath the bed at the start of the path in amounts suflicient to completely ignite the bed but insuificient to combust with a substantial portion of the volatiles liberated from the coal thereabove; zone feeding hot primary air upwardly through the bed from succeeding zonal regions disposed beneath the bed progressively away from the initial zonal region and towards the end of the path in successively decreasing amounts sufiicient to maintain limited combustion within the bed but insufficient to combust with substantial portions of the volatiles liberated from the coal thereabove; simultaneously zone feeding hot, substantially oxygen-free gas upwardly through the bed with said decreasing amounts of air in progressively increasing amounts from said succeeding zonal regions so as to sweep unburned volaties into the oven above the bed; simultaneously feeding hot over-fire air into said oven to combust with said unburned volatiles and thereby create a fireball over the bed and in the furnace mouth, the partial combustion of the unburned volatiles in the bed and the radiation of the fireball heating the coal in the bed progressively upward to maximum temperatures in the range of 1,800 F. to 1,900 B, discharging the hot coke into a substantially oxygen-free confined space in open communication with the oven; maintaining the discharged coke in said confined space until the heat in the coke drives off residual volatiles therefrom; and returning said residual volatiles to above the bed in said oven consumption in said fireball.

5. In a method of producing heat and coke from green plasticisable coking coal, including the steps of preheating the coal to about 350 F. and removing all moisture therefrom; passing a homogeneous bed of the preheated coal in a horizontal path through a coking oven having a furnace mouth over part of the bed path; and igniting the bed as it enters the oven: the improvements which comprise the steps of zone feeding hot primary air upwardly through the bed from an initial zonal region beneath the bed at the start of the path in amounts suificient to raise the bed temperature to approximately 600 F., but insuificient to combust with a substantial portion of the volatiles liberated from the coal thereabove; simultaneously zone feeding hot primary air upwardly through the bed from succeeding zonal regions disposed beneath the bed path and progressively away from the initial zonal region and towards the end of the path in successively decreasing amounts suflicient to maintain limited combustion within the bed but insufficient to combust with substantial portions of the volatiles liberated from the coal thereabove; simultaneously feeding hot, substantially oxygen-free gas upwardly through the bed with said decreasing amounts of air in progressively increasing amounts from said succeeding zonal regions and simultaneously feeding hot, substantially oxygen-free gas alone upwardly through the bed from a terminal zonal region beneath the bed at the end of the path so as to sweep unburned volatiles into the oven above the bed; simultaneously feeding hot overfire air into said oven to com-bust with said unburned volatiles and thereby create a fireball over the bed and in the furnace mouth, the partial combustion of the unburned volaties in the bed and the radiation of the fireball heating the coal in the bed progressively upward to maximum temperatures in the range of 1,800 F. to 1,900 F.; discharging the hot coke into a substantially oxygen-free confined space below and in open communication with the oven; maintaining the discharged coke in said confined space until the heat in the coke drives ofi residual volatiles therefrom; and returning said residual volatiles to above the bed in said oven for consumption in said fireball.

References Cited in the file of this patent UNITED STATES PATENTS 1,591,023 Ditto et a1. July 6, 1926 1,839,741 Davies July 5, 1932 1,918,162 Willson July 11, 1933 2,179,080 Alther Nov. 7, 1939 2,209,255 Andersen et al. July 23, 1940 2,347,076 Boynton et a1. Apr. 18, 1944 2,380,930 Andersen et al July 7, 1945 FOREIGN PATENTS 655,257 France Dec. 17, 1928 

1. IN A METHOD OF PRODUCING HEAT AND COKE FROM GREEN PLASTICISABLE COKING COAL, INCLUDING THE STEPS OF PREHEATING THE COAL UNTIL SUBSTANTIALLY ALL MOISTURE IS DRIVEN THEREFROM AND THE COAL IS DRY; PASSING A HOMOGENEOUS BED OF THE DRIED PREHEATED COAL IN A HORIZONTAL PATH THROUGH A COKING OVEN HAVING A FURNACE MOUTH OVER PART OF THE BED PATH; AND IGNITING PART OF THE BED AS IT ENTERS THE OVEN: THE IMPROVEMENTS WHICH COMPRISE THE STEPS OF ZONE FEEDING HOT PRIMARY AIR UPWARDLY THROUGH THE BED FROM AN INITIAL ZONAL REGION BENEATH THE BED AT THE START OF THE PATH IN AMOUNTS SUFFICIENT TO COMPLETELY IGNITE THE BED BUT INSUFFICIENT TO COMBUST WITH A SUBSTANTIAL PORTION OF THE VOLATILES LIBERATED FROM THE COAL THEREABOVE; SIMULTANEOUSLY ZONE FEEDING HOT PRIMARY AIR UPWARDLY THROUGH THE BED FROM SUCCEEDING ZONAL REGIONS DISPOSED BENEATH THE BED PROGRESSIVELY AWAY FROM THE INITIAL ZONAL REGION AND TOWARDS THE END OF THE PATH IN SUCCESSIVELY DECREAS- 